The present invention is an explosion prevention system for use with gas burning appliances of the type having automatic ignition apparatus integral therewith. More specifically, the present invention is a system which continuously samples the atmosphere and, in response to the potentially explosive presence of fuel-gas, automatically blocks passage of gas into the gas distribution system and simultaneously disables the appliance ignition apparatus to attenuate the danger of an explosion.
The high cost of energy has made it incumbent on energy users to investigate the feasibility of use of various fuels, depending on cost and local availability. Because they are easily interchangeable, with respect to distribution systems and combustion devices, various fuel-gases have been considered. Although fuel-gases often have favorable cost factors when compared with normally liquid petroleum products, the danger of explosion from leaking fuel is generally greater.
Depending on geographic location, one particular fuel-gas, propane, has been found to have a favorable cost per B.T.U. factor compared with other gases, in part because it can be inexpensively shipped in liquefied form under pressure. However, this fuel-gas product suffers from a disadvantage over other gases in that it is heavier than air and thus more likely to be contained in a cellar enclosure. If leakage occurs, an explosion is almost inevitable if the accumulation goes unnoticed. With lighter than air gases, an explosive accumulation is also an ever present hazard especially where ventilation is minimal or lacking altogether.
Although gas detector alarms are known, these devices fail to provide the necessary safeguards for use with gas appliances. Gas detector alarms provide an indication of a potential hazard but do nothing to attenuate the hazard. It is important that fuel leakage be stopped and any automatic ignition devices be disabled. This will prevent further dangerous accumulations of gas, and also prevent explosive ignition of the already accumulated gas, by the gas appliance ignition system.
We are unaware of any system which simultaneously closes off the fuel supply and disables the appliance ignition system, thus to stop any leakage and prevent accidental ignition of accumulated gases. Just closing off the fuel supply will stop the leak and eventually cause most appliances to eventually shut off, due to internal safety control. However, appliance safety controls normally operate by activating the ignition device and sensing if a flame is present. If no flame occurs, for example if no fuel is available, the safety controls will shut down the system. As is readily evident, if a fuel gas has accumulated in the area of the appliance, the appliance ignition system can ignite it to cause an explosion. On the other hand, if only the appliance ignition system is disabled, the gas will continue to leak and may be accidentally ignited by other means than the appliance. An alarm by itself serves only to warn of danger but does nothing to alleviate the possibility of an explosion. Thus, in order to prevent an explosion from gas leakage, one must stop the leak and disable possible sources of ignition.